Does It Only Take 3 Weeks to Form a Habit?

Rethinking the popular claim that habits form in 21 days

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I've heard it said hundreds of times. From patients, from colleagues, and sometimes from the media: "It takes three weeks to form a habit." But in my experience, both personally and professionally, the notion that true habits—behaviors that persist in the face of major life upheavals and adversities—can be forged in 21 days flies in the face of reality. So I decided to research the claim.

My readings took me to a self-help book written in 1960 by Maxwell Maltz, a cosmetic surgeon, who reported that it took 21 days for amputees to stop feeling phantom limb pain. Maltz then extrapolated that consciously cultivating a new behavior for just 15 minutes a day for 21 days could create a habit. This didn't strike me as particularly rigorous or convincing proof.

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Looking to more modern research wasn't any more helpful. The most recent piece I could find was a 2009 study published in the European Journal of Social Psychology that looked at the time it took for subjects to "automate" an eating, drinking or exercise behavior "carried out daily in the same context"—i.e., a habit. And with examples such as the time it took to automatically drink a glass of water after waking, or to do 50 sit-ups before breakfast, they concluded that it took participants between 18 and 254 days for these behaviors to happen "automatically."

That's one heck of a spread. Given that the study didn't control for the real-life upheavals that tend to get in the way of our very best intentions, and that the behaviors chosen are so minor in scope, I don't think the results are applicable to the real world, let alone to the prospect of cultivating an entirely new lifestyle, replete with perhaps dozens of new and more complex behaviors and choices.

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Ex-smokers are a great group to chat with about how long it takes to make or break a habit. According to the National Institutes of Health, nicotine's physiologic withdrawal symptoms are usually over within a week. Yet, as any ex-smoker will tell you, the fight not to smoke (to break the habit of smoking and cultivate that of not smoking) lasts much longer.

[See Is It Possible to Be Smoke Free in 30 Days?]

I was a smoker once. I smoked a pack a day for nearly seven years, and I vividly remember how difficult it was to quit. As have many, I quit cold turkey and the first few weeks were truly miserable, with a nearly constant, conscious battle not to smoke.

As time went by, the battles became less frequent. However, astonishingly to me, even two to three years after quitting, there were still occasional moments or circumstances when I had to consciously fight the urge to light up. And while it's been more than 20 years since I've had a puff, and while I no longer have to consciously fight any urges, I've no doubt that if I started again, I'd be back to a pack a day in no time.

What I'm getting at is that changing behaviors and creating new habits takes an awfully long time. While you may well be able to establish a comfort level with a new behavior in just 21 days, my experiences have taught me that habit formation requires years of consciously reminding yourself of your new choices.

True, the longer you sustain a behavior, the less frequent the need for conscious reminder. But I can't help but wonder how many people's best intentions were lost because they believed they'd forged a habit, when really they just planted a new behavior.

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So whatever it is you're trying to accomplish, why not take advantage of the world that we live in and layer some conscious reminders into your life? Smartphones, computers, and even old-school sticky notes can be employed to take some of the pressure off of you constantly remembering. And while it may seem tedious to keep your new behaviors in regular focus, if you truly want to forge a new habit, a year or two of tedious reminding is a relatively small price to pay.

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Hungry for more? Write to eatandrun@usnews.com with your questions, concerns, and feedback.

Yoni Freedhoff, MD, is an assistant professor of family medicine at the University of Ottawa, where he's the founder and medical director of the Bariatric Medical Institute—dedicated to non-surgical weight management since 2004. Dr. Freedhoff sounds off daily on his award-winning blog, Weighty Matters, and is also easily reachable on Twitter. Dr. Freedhoff's latest book Why Diets Fail and How to Make Yours Work will be published by Random House’s Crown/Harmony in 2014.